Four-way change-over device for hydraulic installations



y 1969 I H. K. CHRISTENSEN 3,443,586

FOUR- WAY CHANGE-OVER DEVICE FOR HYDRAULIC INSTALLATIONS Filed June 7,1967 Sheet of s ,jjigil INVENTOR. //L 6 h. ("Aw/J TEA/SEN May 13, 1969FOUR-WAY CHANGE-OVER DEVICE FOR HYDRAULIC INSTALLATIONS .Filed June 7,1967 H. K. CHRISTENSEN Sheet 7 42 W I II I j v A //Z% %/ALW C) O O O O 37 I L! 3 I INVENTOR. f aez fffs e/snm/aa/v H. K. CHRISTENSEN 3,443,586

' FOUR-WAY CHANGE-0VER DEVICE FOR HYDRAULIC INSTALLATIONS Filed June 7,1967 Sheet i of 3 INVENTOR. H5465 hf (H/W: TEA/JEN United States Patent50,258 Int. Cl. F16]: 11/02; F010. 21/14 US. Cl. 137-59612 14 ClaimsABSTRACT OF THE DISCLOSURE The invention is a control for ahydraulically operated motor which in general facilitates changing thedirection of operation of the motor and provides a neutral position. Inaddition, the control has a manual and an automatic throttling functionfor controlling the speed of the motor and for controlling the volumeand pressure of the pressurized fluid delivered to the motor.

More specifically the invention relates to a four-way change-overdevice, for hydraulic installations comprising a delivery pipe, a returnpipe and two working ducts which lead to the hydraulic machine viachange-over orifices.

Such change-over devices are necessary, in order to achieve dynamicreversal for a hydraulic machine, for example a motor. To achieve thispurpose, in a first working position the delivery pipe is connected toone of the working ducts, and the return pipe to the other working duct,where-as in a second working position these connections are reversed.Frequently the change-over devices can be switched to neutral in whichposition the delivery pipe and the return pipe are connected to oneanother through a bypass duct.

Conventional change-over devices merely perform a change-over function.If, in addition to this, the volume of flow which passes through thehydraulic machine is to be varied, for example in order to control thespeed of the motor, a throttle valve is used which is inserted in thedelivery pipe. However this throttle varies the pressure characteristicsin such a way that linear control is not possible. Besides, severalmanipulations are necessary to operate the hydraulic machine. If thechange-over device is operated while the motor runs, the latter, orparts connected thereto, may suffer damage due to the forces of inertia.Moreover, the number of connecting pipes and of connections rises withthe number of devices used, so that the lay-out of the hydraulicinstallation becomes more complicated. This is an importantconsideration in view of the fact that, in addition to theabove-mentioned switching and control devices, usually also safetydevices are provided, for example an overpressure valve inserted betweendelivery pipe and return pipe, and a non-return valve shunting thechange-over device.

The present invention has for its object, to obviate the above-mentioneddisadvantages entirely or partly.

The invention is based on a four-way change-over device of the typereferred to and is characterized by a bypass duct effective in theworking position of the de vice, a throttle device being incorporated inthe said bypass duct which can be varied in dependence on thechange-over displacement in such a way that the throttle resistanceincreases as the clearance of the change-over orifices is enlarged.Preferably the bypass duct is of a type such as used in knownchange-over devices, where it is operative in the neutral position.

In this way a device is obtained which not only performs a change-overoperation but also enables the volume of flow to be controlled. Thefurther the change-over ice device is displaced from neutral, the moreeffectively will the bypass duct be throttled, Le. a larger volume ofworking fluid is directed towards the machine. Actuation of the deviceis by a single manipulation such that when this manipulation is effectedby way of a continuous displacement, the volume of working fluid fed tothe machine varies continuously from a positive maximum to a negativemaximum. The direction of flow is reversed when the volume of flow isnear zero, so that the moments of inertia during reversal are low.Furthermore, control via the bypass duct makes it possible to achieve asubstantially linear volume variation for the working fluid during theadjustment. Finally, the device of the invention oper-ates with onlyfour connections. No pipes are needed between the change-over device anda separate flow control device.

In a preferred embodiment of the invention the throttle resistance, orat least part of this resistance in the bypass duct is variable also independence on the pressure drop of the working fluid in the bypass duct.This has the effect of improving the linearity of the flow volumecharacteristic. In particular, the throttle device in the bypass ductmay be provided with a pressure-dependent throttle point in series witha shift-dependent throttle point. In that case the two throttlefunctions are clearly separated and can each be easily calculated,designed and adjusted apart from one another.

In this context it may be advisable to let the pressuredependentthrottle consist of two control orifices in front of and behind acontrol pressure chamber both of which orifices close as the pressuredrop increases, and to control this throttle point in dependence on thepressure drop at the control orifice behind this chamber and at theseries-connected, shift-dependent throttle.

The design is simplified if the change-over device is a rotary slide inthe case of which not only the orifices required for the change-overfunction, but also the orifices for the shift-dependent throttle of thebypass duct are provided on the control surface, for example on thecircumference. As -a result of the displacement from neutral thecross-sectional area of the change-over orifices is increased, whereasthe cross-sectional area of the throttle orifices provided on the samecontrol surface is reduced.

In further development of the invention the rotary slide may be acylindrical hollow element in the cavity of which the pressure-dependentthrottle is arranged. This embodiment offers the further possibility ofaccommodating in the cavity also an overpressure valve and/or anon-return valve. This possibility exists not only because the cavityoffers sutficient space for this purpose, but also because all ductsrequired for the connection of these valves converge in the device. Ifthis concept is carried to its extreme, a single device between pump andmachine which caters for all switching, control and safety arrangementswill be sufficient, and this constitutes a considerable simplificationin the lay-out and assembly of the hydraulic installation.

In a preferred embodiment the change-over device is designed in such away that, in known manner, the control surface of one part of the rotaryslide is provided with first and second orifices, for examplelongitudinal grooves, which, in circumferential direction arealternately connected with the delivery pipe and the return pipe, whilethe control surface of the other part of the rotary slide is providedwith first and second orifices on lines axially displaced relative toone another of which the orifices on one line communicate with one ofthe working ducts and the orifices on the other line with the otherworking duct but which are displaced relative to one another by thecircumferential division of the orifices of the other part (change-overorifices), and that in the control surface of one part of the rotaryslide there are provided third orifices communicating with the deliverypipe which cooperate with third orifices on the control surface of theother part of the rotary slide and are connected to the return pipe,their largest cross-sectional area becoming available in the neutralposition (shift-dependent throttle).

For the actual construction of the pressure-dependent throttle werecommend a spring-loaded, hollow plunger provided in the cavity of theinner component of the rotary slide, which is axially displaceable andenvelops the control pressure chamber and is influenced by the dischargepressure as well as by the higher pressure in the control chamber andwhich is provided in its wall with first control orifices cooperatingwith ducts in the inner rotary slide component so as to constitute thepressuredependent throttle, the said ducts communicating with theshift-dependent throttle and the return pipe. The wall of the plungermay be provided with second control orifices cooperating with ducts inthe inner rotary slide component so as to provide a furtherpressure-dependent throttle, the said ducts communicating with thedelivery pipe.

In an embodiment giving a very short axal length provides for the thirdorifices of one of the rotary slide components to be arranged axially inline with the first orifices and on the same circumferential line as theends of the second orifices.

In further development of the invention the case of the rotary slide maybe a cylindrical insert situated in a fixed case, the latter case beingprovided with the connections. Such an insert can be much more easilymachined than the case itself. Besides, also a rotary-slide casing whichis already available for other purposes may be used in which caseadaptation of the fixed rotary-slide compo nent is achieved by thedesign of the cylindrical insert.

Advantageously, a peg passes through radial apertures in the case, inthe cylindrical rotary-slide insert and in the interior rotary-slidecomponent, the apertures in the inner rotary-slide component being of asize permitting of a limited angular displacement of the lattercomponent relative to the cylindrical rotary-slide insert or the case.In such an arrangement the peg serves not only as a fixing means, butalso limits the angular displacement between the two rotary-slidecomponents, i.e. it determines the range of displacement.

One embodiment of the invention is characterized by an open sector inthe inner as well as the outer rotary-slide component, both sectorshaving substantially the same angle, and by a volute spring with twobent ends which engage the open sectors and, in the relaxed condition,enclose a slightly larger angle, one of the ends being led through thespring coil into the plane of the other. Such a spring is of short axiallength and holds the two rotaryslide components in their neutralposition with a slight bias. The rotary slide can be turned against theforce of the spring in one or the other direction, the loading of thespring being the same in each direction.

The invention will now be described in further detail with reference toan embodiment thereof given by way of example and illustrated in thedrawings. There are shown 1n:

FIG. 1 a fiow diagram of a hydraulic installation comprising the deviceof the invention;

FIG. 2 the device of the invention in plan view, without end plate andbolts;

FIG. 3 the device of the invention in longitudinal section, mainly alongthe vertical centre line and, only in the upper part at the level ofline A-A, through the connections for the delivery and return pipes;

FIG. 4 a cylindrical rotary-slide insert in plan view;

FIG. 5 the inner rotary-slide component in elevation;

FIG. 6 the inner rotary-slide component in vertical section;

FIG. 7 a development of the control surface of the inner rotary-slidecomponent (outer circumference);

FIG. 8 a development of the control surface of the rotary-slide insert(inner circumference);

FIG. 9 a part-sectional view along the line BB of FIGURE 3, and

FIG. 10 a side view of a return spring.

The flow diagram of FIGURE 1 shows a pump 1 which is driven at constantspeed by a motor 2 and conveys working fluid to the device of theinvention 4 via a delivery pipe 3. From this device a return pipe 5 istaken to the reservoir 7 via a filter 6. A hydraulic machine 8, forexample a motor, is connected to the device 4 through two working ducts9, 10. The device 4 is therefore provided with a connection 11 for thedelivery pipe 3, a connection 12 for the return pipe 5, and twoconnections 13, 14 for the working ducts 9, 10. From the device 4projects a rotatable shaft 15 by means of which the working fluidpassing through the motor can be controlled as regards its volume offlow and also its direction.

The device of the invention comprises a case 16, shown in FIGURE 2 inplan view, which is provided with the delivery pipe connection 11, thereturn pipe connection 12, and the two working duct connections 13 and14. The casing comprises an axially symmetrical cavity 17, indicated bybroken lines, of which only section 18 and section 19, the latter with asomewhat enlarged diameter, are relevant to the invention. From the fourconnection points 11-14, four ducts 20-23 lead to the cavity 17 in sucha way that duct 21 terminates in section 19, whereas duct 20 terminatesat the opposite end of section 18, and the ducts 22, 23 terminate atdilferent points of a central region.

In the cavity sections 18, 19 is inserted a rotary-slide insert 24. Atits outer circumference it is provided with four circumferential grooves25-28 at an axial distance from one another such that thecircumferential groove 25 communicates with the duct 20, thecircumferential groove 26 with the duct 22, the circumferential groove27 with the duct 23 and the circumferential groove 28 with the duct 21.Consequently, the circumferential groove 25 communicates with thedelivery pipe, the circumferential groove 26 with one of the workingducts, the circumferential groove 27 with the other working duct and thecircumferential groove 28 with the return pipe. The change-overfunctions are performed by the first orifices 29 in the circumferentialgroove 26 and the second orifices 30 in the circumferential groove 27.Throttling within the bypass duct is effected by the third orifices 31in the circumferential groove 28. The orifices 32 in the circumferentialgroove 28 and the orifices 33 in the circumferential groove 25 merelypass liquid and have no proper control function of their own.

The inner rotary-slide component 34 (FIGS. 5 and 6) consists of acylindrical hollow body whose cavity comprises essentially alarge-diameter section 35 and a smalldiameter section 36. To the holder37 may be attached a handle 15 for rotation. The outer diameter of therotaryslide component 34 which, together with the inner circumference ofthe insert 24 constitutes the actual control surface, is provided withfirst orifices in the shape of longitudinal grooves 38 and, displacedrelatively thereto in circumferential direction, second orifices in theshape of longitudinal grooves 39 all of which function in thechange-over operation. Furthermore, third orifices 40 are provided asterminations of the ducts 41 which participate in the throttlingfunction. The orifices 40 are arranged in line with the longitudinalgrooves 38 and on the same circumferential line as the ends of thelongitudinal grooves 39. A circumferential groove 42 enablesdistribution of the pressure fluid in the longitudinal grooves 38. Bores43 lead from the circumferential groove to the extreme front section ofthe cavity of the rotary-slide component 34. From the longitudinalgrooves 38, bores 44 lead to the section 35 and bores 45 to the section36. From the longitudinal grooves 39, bores 46 lead to the section 35.The inner terminations 47 of the duct 41, and 48 of the duct 45, areidentified here, because they participate in the pressure-dependentthrottling operation. Finally, a bore 49 connects the left end of thecavity 36 with return pressure in the section 19 of the casing.

Inserted in the cavity section 36 is a hollow plunger 50, loaded at oneend by a spring 51 and the return pressure prevailing in the chamber 52and, at the other end, by the pressure prevailing in the controlpressure chamber 53. In the wall of the plunger 50 is provided a firstcontrol orifice in the shape of a circumferential groove 54 and a secondcontrol orifice in the shape of a circumferential groove 55. Both thesecircumferential grooves communicate with the control pressure chamber 53via bores 56, 57. The first control orifice 54 cooperates with theorifices 47 of the ducts 41, being the first pressure-dependentthrottling point, whereas the second control orifice 55 cooperates withthe orifices 48 of the ducts 45, being the second pressure-dependentthrottling point.

Inserted in the cavity section 35 is an overpressure valve 58 which maybe of any desired type and which opens when the pressure betweendelivery pipe and return pipe exceeds a predetermined value. In thepresent case a cartridge is used which causes any overpressure which mayexist in the chamber 80 to displace a first valve element 59 against theforce of a spring. The pressure which then builds up underneath theactual valve element 60 lifts the latter from its seat 61. The wholeassembly is held in the rotary slide 34 by means of a retainer 62.

As becomes apparent from FIG. 9, the right-hand end face of the case 16is provided with a recess 63 at each one of opposite points in which apeg 64 is placed during assembly. This peg is fixed by the end plate 65of the housing when the latter is secured by means of screws 66. The pegpasses through two recesses 67 provided on the end faces of the insert24, and through two open recesses 68 on the end face of the innerrotary-slide component 34, the said recesses being of enlarged,sector-shaped crosssection. The angular displaceability of therotary-slide section 34 is thus limited relative to the insert 24.Furthermore, the two rotary-slide components 24, 34 are provided withsector-shaped recesses, 69, 70 at their end faces which enclose an angleof substantially the same value. The two ends 71, 72 of a volute spring73 apply themselves to the walls of these recesses, forcing therotaryslide component 34 into its neutral position, while allowing it tobe turned against the force of the spring. When the spring 73 isrelaxed, the two ends 71, 72 enclose a slightly larger angle than thatdetermined by the sector shaped recesses 69, 70. The spring end 72 istaken into the plane of the other end 71 through the spring coil itself.The spring 73 is likewise prevented from dropping out by the peg 64.

To explain the operation of the device, I refer to FIGURES 7 and 8 whichshow developments of the outer circumference of the inner rotary-slidecomponent 34 and of the inner circumference of the insert 24. For thepurpose of the embodiment illustrated here it should be assumed that theseveral control orifices are distributed three times over thecircumference, i.e. that they are spaced apart from one another by anangular distance of 120. The component 34 is rotatable relative to thecomponent 24 in the directions indicated by the double-arrow P.

Through the orifices 33, fluid is fed at pump pressure to thecircumferential groove 42 and the longitudinal grooves 38. With thedevice in the neutral position, the orifices 31 and 40 of the throttleassembly coincide, whereas the longitudinal grooves 38 and 39 aresituated every time between the orifices 29 and 30. Therefore the entirevolume of fluid delivered by the pump passes via the longitudinalgrooves 38, the bores 45, the pressure-dependent throttle 48, 55, thecontrol pressure chamber 53, the pressure-dependent throttle 54, 47, theduct 40 and the completely open, shift-dependent throttle 40, 31 towardsthe return connection. When the slide component 34 is rotated a little,the longitudinal groove 38 begins to communicate with one of theorifices 29, 30, while the longitudinal groove 39 begins to communicatewith the other orifice. Therefore an amount of pumped fluid whichdepends on the size of the change-over clearances 38, 29 and 39, 30 isnow enabled to pass to the motor. At the same time, the clearcross-section of the shift-dependent throttle 31, 40 has become reduced,so that in the bypass duct an increased throttle resistance becomesoperative. Consequently, the pressure drop across the bypass ductremains substantially constant, notwithstanding the reduced volume ofworking fluid passing through it, while the working pressure remainssubstantially constant. This mode of operation does not depend onwhether the slide component 34 is rotated clockwise or anticlockwise.The longitudinal grooves 39 communicate in each case with the returnside through the orifices 32.

Apart from the shift-dependent throttle 31, 40, I have still to considerthe pressure-dependent throttle 48, 55 and 47, 54 in the bypass duct. Asthe pressure drop across the two throttles 47, 54 and 48, 55 increases,the plunger 50 is displaced towards the left. In this way, the throttleresistance of the pressure-dependent throttle 48, 55 grows, so that thepressure drop across the pressure-dependent throttle 47, 54 and acrossthe shift-dependent throttle 31, 40 remains substantially constant.However, as the pressure rises, also the throttle resistance at thethrottle 47, 54 is increased. This is to compensate for the fact that,with increasing pressure, the leakages of the hydraulic devicesincrease, so that, if the desired output is to be maintained by thedevice, it becomes necessary to pass a somewhat increased amount ofworking fluid through the machine than would correspond to a linearrise.

When overpressure occurs between the delivery pipe and the return pipe,the overpressure valve, 58 opens. The principle of the invention can ofcourse also be applied to a rotary slide in which the end faces are usedas control surfaces. It would also be possible to employ a flat slide,or to couple the displacement of the changeover valve with an adjustmentof the throttle resistance in a bypass duct in some other way.

I claim:

1. A four way change-over fluid pressure control device of the typehaving inlet and outlet ports and two control ports which arealternately connectable to opposite ports of a hydraulic load devicesuch as a motor, comprising rotary valve control means having passagesfor selectively and alternately connecting said control ports to saidinlet and outlet ports in a graduated rnanner from fully closed to fullyopened positions, bypass means between said inlet and outlet ports, andthrottle means in with said bypass means operable in response to saidcontrol to gradually increase the resistance of said bypass means assaid control ports are opened by said control means.

2. A fluid pressure control device according to claim 1 wherein saidcontrol means has a neutral P sition and said bypass means connects saidinlet and outlet ports to provide fluid flow therebetween when saidcontrol means is in a neutral position.

3. A fluid pressure control device according to claim 1 having secondthrottle means in with said bypass means for providing additional fluidflow resistance in response to an increase in the pressure drop of thefluid flowing in said bypass means.

4. A fluid pressure control device according to claim 3 wherein saidfirst and second throttle means are arranged in series and said secondthrottle means is shiftable relative to said control means.

5. A fluid pressure control device according to claim 4 wherein saidsecond throttle means is on the upstream side from said first throttlemeans and has a chamber with inlet and outlet control orificescommunicating with said inlet port when said control means is in aneutral position and said orifices are gradually closed as said secondthrottle means is shifted relative to said control means.

6. A fluid pressure control device according to claim 1 wherein saidcontrol means includes a rotary slide valve having on the circumferencethereof passages for selectively supplying and exhausting fluid to andfrom said control ports and having upstream and downstream axiallyspaced sets of orifices forming a part of said first and second throttlemeans.

7. A fluid pressure control device according to claim 6 in which saidrotary slide valve has a cylindrically shaped bore portion in which saidsecond throttle means is slidably disposed.

8. A fluid pressure control device according to claim 7 wherein saidrotary slide valve has a second cylindrically shaped bore portion, and apressure relief valve disposed in said second bore portion which isoperative when the pressure difference of the fluid in said inlet andoutlet ports exceeds a predetermined value.

9. A fluid pressure control device according to claim 6, said fluidpressure control device comprising a casing defining a cylindricallyshaped cavity, an annularly shaped valve member fixedly disposed in saidcavity and having a bore in which said rotary slide valve is slidablydisposed, said passages of said rotary slide valve comprising two setsof alternately and circumferentially arranged axially extending grooveswith said sets being in respective fluid communication with said inletand outlet ports, said annularly shaped valve member having two sets oforifices which are axially and circumferentially spaced from each otherand which have respective fluid communication with said control ports,said annularly shaped valve member having a third set of orificescommunicating with said outlet port and said downstream set of throttleorifices of said rotary slide valve, said third set of orifices beingfully aligned with said downstream set of throttle orifices when saidrotary slide valve is in its neutral position.

10. A fluid pressure control device according to claim 7 in which saidsecond throttle means has the form of a hollow plunger closed at one endthereof, spring means in said cylindrically shaped bore portion of saidrotary slide valve for biasing said plunger in an axial directionagainst the fluid pressure differential existing between the fluidflowing from said inlet port to said outlet port, said plunger having afirst set of orifices in the wall thereof which cooperate with saidupstream set of orifices of said rotary slide valve and said inlet portto effect increased and decreased throttling of the inlet fluid inresponse to axial movement of said plunger.

11. A fluid pressure control device according to claim 10, where saidplunger has a second set of orifices in the wall thereof havingcommunication with said downstream set of orifices of said rotary slidevalve and said outlet port to effect increased and decreased throttlingof the inlet fluid in response to axial movement of said plunger.

12. A fluid pressure control device according to claim 9 in which saiddownstream set of orifices of said rotary slide valve are arrangedaxially in line with said set of grooves which are in fluidcommunication with said inlet port.

13. A fluid pressure control device according to claim 1 wherein saidcontrol means comprises a rotary slide valve having a neutral position,means for limiting the angular displacement of said valve in oppositedirections from said neutral position to effect the selective andalternate supplying and exhausting of fluid to and from said controlports.

14. A fluid pressure control device according to claim 13 in whichspring means are provided to maintain said rotary slide valve in itsneutral position.

References Cited UNITED STATES PATENTS 1,947,973 2/1934 Davis l3'7625.242,239,139 4/1941 Allin 137--596.l2 XR 2,499,425 3/1950 Stephens137596.l2 2,607,558 8/1952 Wright l37596.12 XR 2,893,357 7/1959 Clarke137596.l2

HENRY T. KLINKSIEK, Primary Examiner.

US. Cl. X.R. l37--625.24

